1. Field of the Invention
The present invention relates to an apparatus for inspecting a blur correction camera which can correct an image blur caused by, e.g., a camera shake generated in a photographing operation, the blur correction camera, and a method of inspecting the blur correction camera.
2. Related Background Art
As conventional blur correction cameras of this type, the following blur correction camera is known. An angular velocity detecting circuit using, e.g., an angular velocity sensor detects at least the angular velocities caused by vibrations in two directions on a plane perpendicular to the optical axis of the camera. A blur correction lens (anti-vibration lens) as a part of a photographing lens is shifted in substantially the same directions as the detecting directions, thereby moving the optical axis of a photographing optical system. The photographic optical system is driven by decelerating the rotation of an actuator such as a motor using gears and the like and converting the rotation into a linear motion. With these operations, an image blur caused by a vibration generated in the camera can be corrected (this control will also be referred to as anti-vibration control hereinafter).
Such a camera is manufactured while being divided into some portions (partial assemblies) in its manufacturing process, and the partial assemblies are fully assembled after their operations are checked. For example, a correction lens shift mechanism system for shifting the blur correction lens by rotating a motor is assembled in a camera main body after checking whether it normally operates as a single partial assembly. The same applies to the angular velocity detecting circuit for detecting angular velocities caused by a camera shake.
However, the above-mentioned conventional blur correction camera suffers the following problems.
First, the correction lens shift mechanism system and the angular velocity detecting circuit often perform abnormal operations when they are assembled in the camera main body or cannot often provide satisfactory operation performance although they are Good in the operation check process as partial assemblies. In the fully assembled state of the camera, the checking operations cannot be performed.
Second, the output from an angular velocity sensor used in the angular velocity detecting circuit suffers an individual difference (a variation among devices), and the output value of each angular velocity sensor upon reception of a predetermined angular velocity is not constant. Also, an amplifier in the angular velocity detecting circuit suffers a gain variation. Furthermore, the output value from the angular velocity detecting circuit is often converted into a digital value by, e.g., an internal A/D converter of a microcomputer. The A/D converter also suffers an individual difference, and a digital value obtained by A/D-converting a predetermined input voltage is not constant. Note that it is not so difficult to adjust the gain variation of the angular velocity detecting circuit in the state of the partial assembly. However, in this case, an error caused by a variation of the A/D converter still remains. When blur correction is performed in a state with the gain variation, blur correction cannot be performed with high precision.
Third, the angular velocity sensor used in the angular velocity detecting circuit is supported in a space by a vibration member wire-shaped support member for determining the direction of an axis in which the angular velocity of the rotation is to be detected, as disclosed in Japanese Laid-Open Patent Application No. 2-228518. A case of the angular velocity sensor, to which legs of the support member are fixed, has a structure that can easily cause an individual difference of the detection axis. Furthermore, errors of the mounting direction occur in a process of mounting the angular velocity sensor in the angular velocity detecting circuit and in a process of assembling the angular velocity detecting circuit in the camera main body. With these errors, a deviation is generated between the detecting direction of the angular velocity of the angular velocity detecting circuit and the moving direction of the optical axis which is attained by actually shifting the blur correction lens (this deviation will also be referred to as a detection angular deviation since the deviation in the detecting direction of the angular velocity detecting circuit is dominant). The angular deviation is often as large as 5.degree. or more. As described above, when the detecting direction of the angular velocity and the moving direction of the optical axis have an angular deviation therebetween, blur correction cannot be performed with high precision.